An overview of the DMSobservations with
image intensified videosystems
is presented.
Double-station video results such asorbital elements and trajectory data
are maintained on our DMS ftp-site
and are ready for download.

Last updated: April 17, 2003

DMS video setupsDMS Video Observations and Results

Within DMS video observations started around 1987.
Active members in this field are:
Klaas Jobse,
Hans Betlem,
Romke Schievink,
Carl Johannink,
Jan Boonstra,
Casper ter Kuile and
Marc de Lignie.
The video cameras used are typically equipped with an F/1.2-55 mm photographic
objective, a Hi8 camcorder and military image intensifying electronics (see below).
Such a camera records stars up to magnitude +8 and meteors up to magnitude +7 in a
25 degrees field of view. The mass range in detected meteors is thus distinctly
different compared to photographic observations and observations are worthwhile
even with low hourly rates of a certain stream.

The AEG XX1400 Microchannel Image Intensifier Tube used at station Biddinghuizen.
Some general characteristics:

DMS has focussed their efforts exclusively on double-station
observations and in some cases meteors were even recorded by three cameras
simultaneously. Such observations are more selective than single station observations;
this selectivity is particularly useful for minor showers and for shower outbursts.

The first step in the data reduction is to prepare a list of meteors
that appeared in the video cameras at two or more stations. Then the meteor images are
digitized with a frame grabber, so that they become accessible for computer measurements.
Within DMS this astrometrical reduction is done with the
AstroRecord
computer program. As a final step the atmospheric trajectory and the heliocentric orbit
are calculated for the meteor. The video double-station events recorded by DMS are
measured with an accuracy of 45 arc seconds. This is only a factor four less accurate
than for good quality photographic negatives.

The picture on the left shows the measurement window of the AstroRecord software developed
by Marc de Lignie. Note the blue colored measurement points of the breaks of the meteor trail.
At the right the equatorial coordinates of the measurement point are given. These are computed
after measuring a number of stars.

In the amateur meteor world DMS
pioneered the field of video registration techniques with observations dating back
as far as 1987. Although these observations made immediately apparent the enormous
possibilities of video observations, at that time the computer technology
accessible to amateurs was not suitable to reduce the video images. As a result
it took six years to develop the necessary software and publish the first
astronomically significant results in 1993. Since that time, results from video
observing campaigns by DMS have been published on a regular basis.

Publications and online databaseDMS Video Observations and Results

The table below gives a complete overview of the published
double-station video results by DMS. With 248 major shower members and 38 minor
shower members the sample gives a good overview of stream activity in the northern
hemisphere. The results can be downloaded in the form of a table with
orbital elements and trajectory data from the
DMS FTP-site as a
plain text file or as an
Microsoft Excel file.

Double-station video observations in The Netherlands on October 21/22, 1995,
resulted in 67 orbits among which 32 Orionids, 4 Southern Taurids and 3 Leo Minorids.
The corresponding derived shower activities in the form of "video ZHRs"
are given in the table below.

Shower

Ori

S-Tau

N-Tau

Eps Gem

LMi

N

32

4

0

0

3

VHZR

16

2.0

0

0

1.1

By combining the video samples of 1993 and 1995, a larger sample of
Orionid data is obtained than the sample of photographic data in the IAU database.
For even greater accuracy also the photographic Orionids of the DMS photographic
database were added. This results in very accurate values of radiant motion and a
detailed figure of the radiant area (see below). It is clearly visible that the width
of the radiant increases for smaller particles (those observed by video). This is a
real effect, because the uncertainty in the video observations is smaller than the
width of the radiant area.

Sixty-one Orionid radiant points (J2000.0) moved to
solar longitude 208.00, using the radiant motion given above. The squares are the
new video data, the diamonds are the old video data from 1993 and the circles come
from the DMS photographic database.

As in other video samples around 20 October, the Epsilon Geminids
are not present and it is concluded that the activity of this shower must be lower
than currently believed from visual observations. On the other hand, the Leo Minorids
were clearly present and new values for their orbit and radiant position and motion
could be determined, see the tables below.